I GOTS IT =D
OK, I've GOT IT
SF is living in a world where there was a post-nuclear war and he survived this tragedy because he was in his room (safety cupboard) when it happened. Everyone else in the series has their mind dis-rupted form the war. In episode 7. His little brother supposedly went to fight a "war" which i think is just an excuse that his whole family used to get away from the actual bombs being dropped and such. The whole family left SF behind because they thought he was a filthy immigrant (The voice of the radio being his parents being played back in his mind), they made him live in a tiny whole in the wall and told him that he was filthy, SF would mimic his parents now and then: "I shan't play with you until you've had a wash" "I will have no filthy immigrants in this house!" The reason he has salad fingers is because he has no palms, perhaps from the nuclear war. Those "hairs" he had were probably from his family. the last one he found was his from when he lived in the safety cupboard, two were his parents, one was his sister's, and the other was his brother's. If people were wondering why he freaked out in Ep 6. Because the little girl actually spoke, and SF was supposed to be using his imagination for their voices since they weren't supposed to be able to talk and he hadn't heard real voices for probably years. And I'm guessing he likes the taste of sand and all those strange foods because he was fed them when he was living with his parents as a filthy immigrant.